SMZ1500

The Nikon MicroscopyU SMZ1500 Fluorescence Image Gallery features a wide spectrum of photomicrographs captured digitally using a Nikon SMZ1500 microscope coupled to an epi-fluorescence illuminator and the DXM1200 camera system. Specimens include many that exhibit autofluorescence and some that have been stained with exogeneous fluorophores.

Basswood Root

Basswood Root

The heavily foliaged crown produces dark green heart-shaped leaves that reveal glistening undersides when blown by a breeze, and the flowers of the basswood exude a powerful scent in the warm months of June and July. When in bloom, bees appear to forsake other flowers in favor of the sweet nectar of these aromatic trees. Often affectionately referred to as the "bee tree", the honey produced is nearly white in color and is considered to be high quality. Flowers that go to seed form small nutlets that are favored by squirrels. The trunks of old basswood trees are very frequently hollow and many birds and animals nest or den in them. During the winter months, white-tailed deer and cottontail rabbits are known to nibble on the bark and sprouts to derive nutrients. Several species of basswood have long thrived in Europe, and in Roman mythology the basswood was revered as a symbol of conjugal love and fidelity.

Basswood Stem

Basswood Stem

The heavily foliaged crown produces dark green heart-shaped leaves that reveal glistening undersides when blown by a breeze, and the flowers of the basswood exude a powerful scent in the warm months of June and July. When in bloom, bees appear to forsake other flowers in favor of the sweet nectar of these aromatic trees. Often affectionately referred to as the "bee tree", the honey produced is nearly white in color and is considered to be high quality. Flowers that go to seed form small nutlets that are favored by squirrels. The trunks of old basswood trees are very frequently hollow and many birds and animals nest or den in them. During the winter months, white-tailed deer and cottontail rabbits are known to nibble on the bark and sprouts to derive nutrients. Several species of basswood have long thrived in Europe, and in Roman mythology the basswood was revered as a symbol of conjugal love and fidelity.

Biting Louse

Biting Louse

Even though about 3,000 can be listed, different species of Bovicola are generally associated with a particular animal host (often termed host specific) upon which all of its life cycles — including feeding and reproduction — occur. After mating with an adult male, an adult female lays eggs called nits that are cemented onto the hairs or feathers of the host, usually close to the skin. When hatched, the larva looks like a smaller and paler version of the adult, and it is ready to feed. At this stage, the larva is called a nymph and will molt three times over several weeks before maturing into an adult.

Black Rot

Black Rot of Grape

This fungus reproduces with two types of spores: ascospores and conidia (pycniospores). Ascopores are produced in the grape mummy and forcibly discharged into the air, often traveling considerable distances. Conidia are vegetatively reproduced spores that the fungus uses to propagate, and they are spread through rain or irrigation water splashing on the plants.

Blue Mold

Blue Mold Sporangiophores

Molds are members of the Fungi kingdom, and are therefore neither plant nor animal. While many species of mold possess physical features strongly reminiscent of plants, such as stalk-like growths and plant-like cell walls, these resemblances are merely superficial. For example, the cell walls of plants are composed of cellulose, whereas a mold's cell wall is made of chitin. Furthermore, molds have no chlorophyll and are unable to produce their own food by means of photosynthesis. Rather, molds are heterotrophs and must obtain nutrients by consuming organic materials, a process achieved by secreting digestive enzymes that break down food materials into absorbable form.

Brown Dog Tick

Brown Dog Tick

The brown dog tick has a three-host life cycle. When the larva hatches from its egg, it immediately seeks out the first host animal in the cycle to feed upon. After establishing itself on a host, the larva feeds until it is engorged (filled with blood), which usually requires 2 to 7 days. Once engorged, the larva abandons its host and begins to molt. Molting can take anywhere from 5 to 23 days, after which time the larva is referred to as a nymph. The nymph form again seeks out a host and repeats the process: it feeds, leaves the host, and molts a second time. From the second molting, the tick emerges as an adult and proceeds to seek out a host for the third time. An adult female, once engorged, leaves the host to lay her eggs, after which she will die. Typically, each female lays between 1,000 and 3,000 eggs. The eggs incubate for 19 to 60 days, depending on the season, and hatch to begin the life cycle once again.

Buttercup Stem

Buttercup Stem

Buttercup petals are usually glossy bright yellow or white and are spirally arranged in the shape of a bowl. Although distributed throughout the world, these flowering plants are especially common in woods and fields of northern temperate zones. Its genus name Ranunculus means little frog — a tribute to the many aquatic varieties of buttercup plants. About 200 species comprise the buttercup family Ranunculaceae, which includes a few shrubs and vines. The deeply cut leaves are said to resemble a crow's foot, which is another common name for the buttercup. Nearly all buttercups contain alkaloid compounds that are poisonous and can be fatal to humans, pets, and livestock. Well-known buttercup varieties include the marsh marigold and peony.

Cambium Layer

Cambium Layer

Cambium tissue that contains the initial cells is also known as the lateral meristem, which exercises its greatest amount of activity during the growing season. Evidence of these growth spurts can be seen, for example, in the concentric circles found in cross sections of tree trunks (termed annual rings). In many cases, the age of a tree can be estimated by inspecting the annual rings, noting that usually the larger cell formations denote spring and the smaller formations denote the summer months. Weather and environmental conditions during certain periods of time can also be estimated from studying growth patterns recorded in annual rings.

Canine Tapeworm

Canine Tapeworm Scolex

The proglottids pass through the digestive tract of the primary host and are eliminated with feces. Intermediate hosts (generally prey animals) ingest the larval forms when grazing on contaminated grass. Once ingested, the larvae emerge in the digestive tract where they burrow through the intestinal wall into a blood vessel and are carried to muscle tissue or some other organ tissue (various species of tapeworms select different tissues as destinations for the larvae). The period during which the larvae are encysted in the tissue of the intermediate host is known as the cysticercus, or bladder worm, stage.

Carrion Root

Carrion Flower Root

Carrions (after which the carrion flower is named) are members of the milkweed family and are native to tropical areas of southern Africa. The plants possess large flowers which exude an unpleasant odor resembling rotted meat. The odor attracts flies, which helps the plant to reproduce by pollination. The genus Stapelia contains about 60 species of these succulent plants.

Carrot Taproot

Carrot Taproot

This hardy plant is a member of the parsley family and has fernlike leaves that grow above ground. Although typically orange-colored, roots having white, yellow, and purple pigments are familiar in other parts of the world. Carrots contain a high content of water and a very small amount of essential oils upon which medicinal and aromatic properties depend.

Castor Bean Seed

Castor Bean Seed

Although all parts of the castor bean are actually poisonous, it is the seeds that are the most highly toxic. The toxins found within the castor bean are ricin, and Ricinus communis agglutinin, or RCA. Ricin is a strong cytotoxin, meaning that it targets the cells of a particular organ, while RCA is a member of the hemagglutinin class, a toxin that is targeted specifically at red blood cells. If any part of the castor bean is ingested, symptoms of abdominal pain, diarrhea, and vomiting will occur within hours. In addition, severe dehydration, decrease in urination, as well as a drop in blood pressure tend to occur over a period of days. Death is often possible in the absence of appropriate medical intervention.

Clubmoss

Clubmoss

The yellowish, powdery spores of clubmosses contain flammable pollen that was used as flash powder for the first photographic cameras and by theater pyrotechnists. Clubmosses resemble miniature evergreen trees, having upright stems and horizontal branches that contain spore-bearing cones. For hundreds of millions of years, clubmosses survived many climatic and environmental changes. More closely related to ferns than mosses, these plants grew to gigantic proportions and dominated the earth during the Paleozoic era. The decayed matter of these ancient plants comprises a major portion of coal beds worldwide. Although found in temperate areas, these evergreens continue to chiefly thrive in tropical and subtropical regions.

Cork Cells

Cork Cells

A mature cork cell is non-living and has cell walls that are composed of a waxy substance that is highly impermeable to gases and water called suberin. Depending upon the species of woody plant, the cork cell may be filled with air or may contain traces of lignin, tannins, or fatty acids and may vary in thickness from one to the next. Packed closely together, the cells are generally arranged in radial rows. Separation among the cells is achieved by structures arising from the cork cambium called lenticels. These pore-like structures allow gases to be exchanged between the plant stem and the outside environment. The layer of dead cells formed by the cork cambium provides the internal cells of the plants with extra insulation and protection.

Corn Rust

Corn Rust

Infection occurs when a spore falls onto a leaf or stalk and produces a germ tube. The thread-like tube grows along the host surface until it finds an opening, usually entering through a natural pathway such as a microscopic air pore, called a stomate. Branching out within the tissue, the tube forms a network of filaments and sends bulbous protrusions called haustoria to invade cells and absorb nutrients stored in the living cytoplasm. After a few days, the fungus reproduces by generating spores at the center of the infection site. The spore masses erupt through both sides of the leaf, producing visible brownish-red pustules that mature into the characteristic black spores of corn rust.

Corn Smut

Corn Smut

Corn infected with the fungus Ustilago zeae (also known as U. maydis) forms large, swollen, kernel-like globules with soft black flesh covered by a silvery-gray skin. Called huitlacoche (pronounced wee-tlah-KOH-cheh), the native Nahuatl word, this dish is characterized by an inky, mushroom flavor and has apparently been eaten in central Mexico for thousands of years. In the United States, after decades of trying to eradicate corn smut, some farmers are now attempting to grow corn with large corn smut infestations because the fungus is becoming a more popular gourmet food item, drawing much higher prices than healthy corn.

Crown Wart

Crown Wart of Alfalfa

Crown wart disease mainly attacks the many-branched crown of alfalfa plants, which is partially embedded in soil. Infection causes abnormal growths called galls to form along the crown and is the site where reproductive resting spores are produced. During excessively wet conditions, the spores in the decaying crown release motile zoospores that swim to infect nearby plants.

Druse Crystals

Druse Crystals

Druse crystals are a common occurrence in many plants and are usually granular or star-like in shape. Crystal formations that appear needle- or spear-shaped are referred to as raphides. Both are thought to deter herbivory, and a number of species of plants are poisonous to humans, as well as animals, due to the high calcium oxalate content.

Dutchman's Pipe

Dutchman's Pipe Stem

Different species of Aristolochia vine can be found in Southeast Asia and Australia. Several species of the vine provide important food sources for the larvae of the birdwing butterfly, the largest butterfly in the world. The species of vines that are important to the birdwing butterfly have greatly declined in abundance due to urban development, farming, and forestry operations. This has contributed to the dramatic reduction of the birdwing butterfly and has resulted in its placement on the threatened species list. Dutchman's pipe has been introduced to Australia and is proving to be a very destructive species. A. durior is similar to the native species in Australia, but contains different toxins in its leaves, which are poisoning the butterfly larvae that feed on the leaves. Even in the presence of native vine species, the birdwing butterflies are choosing the Dutchman's pipe species. In the land down under, the Dutchman's pipe might be branded as a butterfly killer, but ironically, in its native North American environment it has its own group of butterflies that depend on it to feed their larvae.

Elodea Leaf

Elodea Leaf

Elodea was once commonly used in aquariums. Unfortunately, some of these plants have been dumped into lakes and ponds in non-native regions around the world and have become nuisance species because their virtually uncontrollable growth. The plants form dense mats that choke out native aquatic plants, provide poor habitat for fish, and interfere with aquatic sports.

Ergot

Ergot

Ergotism, a condition sometimes called St. Anthony's Fire, is caused by toxic doses of alkaloids produced by purple masses of spores called sclerotia. The condition is characterized by two sets of symptoms: (1) gangrene with burning pain in the extremities, and (2) convulsions, hallucinations, severe psychosis, and death. It can also cause miscarriages in both humans and other animals.

Fern Sporangia

Fern Sporangia

Sporophyte ferns have two methods of asexual reproduction. One is by vegetative cloning, branching off of the root-like underground stem, or rhizome, often forming large, genetically uniform colonies. The second form of asexual reproduction occurs by spores. These form on the undersides of the leaves in spore cases called sporangia. Clusters of sporangia, or sori, appear as brown spots and may or may not be present on all leaves. Some species have sori on all the leaves, while others have specialized leaves that bear the sori. When the sporangia dry out, they break open, releasing the spores into the wind. Germination begins when a spore falls in a place with proper conditions of heat and moisture.

Fig Leaf

Fig Leaf

Even as the fruit of the fig tree served as a dietary staple among Ancient Greeks, a species of fig tree, F. religiosa, is said to have provided shade for Buddha during his attainment of enlightenment and has been appointed a sacred tree in India. Today, fig trees can be found in the wild and are also grown in ornamental gardens and commercial and private orchards. Furthermore, the Ficus continues to become an increasingly popular indoor houseplant. Some species of fig trees, such as the Banyan of India, have aerial roots extending from their trunks and branches that reach downward into the ground, giving support to its wide, spreading crown of interlacing vines.

Fish Louse

Fish Louse

These crustacean parasites are infamous for their aggressive attachment and feeding behavior, grasping tightly onto their hosts using small spines, hooked appendages, and a pair of large suckers. A feeding louse will pierce and inject digestive enzymes into the skin or gills of a fish using a stylet — a pointed, needlelike structure — and then suck blood, mucus and enzyme-liquefied body fluids from the host. Constant piercing of the fish skin or gills can cause inflammation and leave the damaged site vulnerable to infection by opportunistic bacteria.

Frog Stomach

Frog Stomach

This smooth, delicate amphibian skin is also air-permeable, allowing oxygen to pass through. Although frogs have lungs, the ability to absorb oxygen from moist surroundings is especially useful to frogs that burrow deep or hibernate in underwater mud. Covered with mucus-secreting glands that help to keep their slippery skin stay moist and pliable, some frogs can also secrete a waxy substance to keep body water from evaporating.

Fruit Fly Body

Fruit Fly Body

Both humans and fruit flies are classified as eukaryotes, carrying their genetic material in a distinct nucleus located within each of their cells. Because of this common denominator, the fruit fly, having a very basic level of physiology, is used as a model organism in studies that are applied toward deciphering more complex processes such as those found in humans. Primary areas of application include cellular, developmental, and genetic investigations. Additionally, fruit flies are inexpensive, reproduce easily, and have short life cycles — all factors adding value to their use in model systems research. Currently, the wealth of information that has accrued through longstanding scientific investigation of the tiny insect is being greatly increased by efforts to sequence its genome. Indeed, a number of genes attributable to the fruit fly are very similar to those found in higher eukaryotes, and biomedical researchers are looking toward the fruit fly for clues in understanding human diseases.

Fruit Fly Eye

Fruit Fly Eye

Both humans and fruit flies are classified as eukaryotes, carrying their genetic material in a distinct nucleus located within each of their cells. Because of this common denominator, the fruit fly, having a very basic level of physiology, is used as a model organism in studies that are applied toward deciphering more complex processes such as those found in humans. Primary areas of application include cellular, developmental, and genetic investigations. Additionally, fruit flies are inexpensive, reproduce easily, and have short life cycles — all factors adding value to their use in model systems research. Currently, the wealth of information that has accrued through longstanding scientific investigation of the tiny insect is being greatly increased by efforts to sequence its genome. Indeed, a number of genes attributable to the fruit fly are very similar to those found in higher eukaryotes, and biomedical researchers are looking toward the fruit fly for clues in understanding human diseases.

Generalized Plant

Generalized Plant Stem Cell

Dermal tissues are the outermost layers of the plant. The primary dermal tissue, the epidermis, is found on young parts of a plant such as new growth of stems and leaves. Epidermis is eventually replaced by the secondary periderm, which is composed of phellem, phellogen, and phelloderm. Cork and bark are common examples of periderm tissue.

Grapevine Stem

Grapevine Stem

Grapevines bloom in spring, producing clusters of small greenish flowers that later mature into succulent, globular-shaped berries. The many different varieties — approximately 8,000 — produce black, green, red, or amber grapes.

Herbaceous Plant

Herbaceous Plant Stem

The herbaceous stem is composed of vascular bundles (xylem and phloem) arranged in a circle around a central core of spongy tissue; this spongy tissue is composed of parenchyma cells and is called the pith. Surrounding the xylem and phloem is a layer known as the cortex, which varies in thickness from species to species; surrounding the cortex is the outermost layer of cells, which is called the epidermis.

Hollyhock Rust

Hollyhock Rust

The large, satiny flowers of the hollyhock come in a variety of colors — from pink, red, white, yellow, lavender, and even black — and are set along erect stalks growing between 5 and 9 feet tall. The hollyhock's heart-shaped, wrinkled leaves have hairy undersides and are a favorite food plant of the butterfly caterpillar before it takes wing as an adult. The flowers of this relative of the marshmallow plant are purported since medieval times to have medicinal applications as an emollient and a diuretic. The flowers of A. rosea are also touted to yield good dyes.

Honeybee Head

Honeybee Head

Honeybees possess five eyes comprised of two distinct types, simple and compound. The simple eyes detect only light, darkness, and movement and look like three little black beads across the bee's forehead. The helmet-like compound eyes of this fuzzy creature are comprised of thousands of minute, hexagonal facets and resemble a honeycomb. Each facet is a lens that reaches down to the retina. This construction gives the bee a mosaic view of the world that is revealed in a multiplicity of tiny images.

Horsetail

Horsetail

E. arvense produces two types of hollow-jointed stems. The fertile stems, tipped with a spore bearing cone about one inch in length, emerge in early spring and die back soon after the spores are released. The spent shoots are rapidly replaced by sprouting vegetative stems bearing whorls of green, four-angled, leaf-like branches. Both varieties of shoots are maintained by food reserves that are stored in small tubers produced along the horsetails' extensive root-like system (rhizome). This root system is actually an underground horizontal plant stem that typically penetrates deep into the soil. The tenacious rhizome allows horsetails to form dense colonies that can grow to weed-like proportions and create problems in orchards and hayfields with poorly drained soils. Although generally having very little commercial value, one species of coarse, textured horsetail contains a high content of silica and is utilized in abrasive scouring powders.

Human Liver Fluke

Human Liver Fluke

Like many other parasites, these trematodes have a three host life cycle involving two intermediate hosts and one definitive host. Fluke eggs are introduced into water by means of feces from an infected host. The eggs are consumed by snails, which serve as the first intermediate host. Inside the snails, the eggs can complete their gestation and proceed to hatch. Newly hatched worms, termed cercariae, leave the snail host to live inside fish, the second intermediate host. Burrowing their way through the flesh of a fish, cercariae encyst themselves inside the fish's muscle tissue. The cercariae lose their tails, undergo some additional growth changes, and are subsequently termed metacercariae. The metacercariae reside inside their fish hosts, awaiting introduction to a definitive host. A human (or another fish-eating animal) becomes the final host by eating the raw flesh of an infected fish, and a single infected fish may contain over a thousand of the encysted worms.

Insect Wing

Insect Wing

Insect wings are thought to have evolved from a gill-like thoracic segment present in early insects, which enabled insects to increase the area available for finding food, shelter, and for breeding. While at rest, many insects fold their wings, spread the appendages horizontally, or position them sloped over their backs. A few insects wrap the outstretched wings around their bodies. Insects have either two or four wings, which are used in various ways to coordinate flight, protect the insect, or to attract a mate.

Jelly Blobs

Jelly Blobs

The majority of Bryozoans are marine (several thousand species), but one class, Phylactolaemata, is found exclusively in freshwater. Pectinatella magnifica is one species belonging to this class, and is commonly found in freshwater lakes and rivers in North America. Most people call them jelly blobs or just plain blobs given their appearance. Each colony is a collection of genetically identical organisms (zooids) that exude a protective matrix, a gelatin-like substance made mostly of water that is firm but slimy to the touch.

Lily Late Prophase

Lily Anther Late Prophase

Anthers are the male reproductive structures of flowering plants that produce pollen. Each anther is deeply bilobed, and each lobe contains two structures called microsporangia. At the center of each microsporangium are numerous mother pollen cells that, after undergoing meiosis, form microspores (pollen grains). Nutrients are provided to a developing cell by the columnar tapetum cells that surround each microsporangium. During the late prophase stage, the tapetum cells are usually microscopically visible. Upon maturing, the pollen grains are released by the anther and made available for transport to a female reproductive organ called the stigma.

Lily Division

Lily Anther Second Division

Anthers are the male reproductive structures of flowering plants that produce pollen. Each anther is deeply bilobed, and each lobe contains two structures called microsporangia. At the center of each microsporangium are numerous mother pollen cells that, after undergoing meiosis, form microspores (pollen grains). Nutrients are provided to a developing cell by the columnar tapetum cells that surround each microsporangium. During the late prophase stage, the tapetum cells are usually microscopically visible. Upon maturing, the pollen grains are released by the anther and made available for transport to a female reproductive organ called the stigma.

Lily Tissue

Lily Anther Sporogenous Tissue

Anthers are the male reproductive structures of flowering plants that produce pollen. Each anther is deeply bilobed, and each lobe contains two structures called microsporangia. At the center of each microsporangium are numerous mother pollen cells that, after undergoing meiosis, form microspores (pollen grains). Nutrients are provided to a developing cell by the columnar tapetum cells that surround each microsporangium. During the late prophase stage, the tapetum cells are usually microscopically visible. Upon maturing, the pollen grains are released by the anther and made available for transport to a female reproductive organ called the stigma.

Lily Fertilization

Lily Double Fertilization

The lily, with its definitive reproductive stages, is a favored specimen in microscopy for illustrating normal cell division. Of special interest are cross sections illustrating the anthers at different stages of development, enabling the observer to follow the evolution of microspore mother cells into mature pollen grains.

Lily Flower Bud

Lily Flower Bud

Most members of the lily family are herb-like and are characterized by bulbs, or enlarged underground storage organs, which give rise to fleshy stems and erect narrow grass-like leaves. Many also display beautiful, showy flowers. Several species within this large family are cultivated as food crops and include such staple culinary ingredients as onions, shallots, garlic, chives, and leeks. Additionally, the bulb of the Madonna Lily was cultivated as early as the second millennium, B.C., for use as a medicinal ointment in Asia Minor.

Lily Seed Embryo

Lily Seed Embryo

A plant embryo is actually an immature plant that is surrounded by stored nutritive materials enveloped in a protective seed coat. The embryo typically consists of embryonic roots (radicles), an embryonic stem (hypocotyl), and leaf-like structures (cotyledons). Lilies are classified as monocots because they produce only a single cotyledon. This embryonic leaf absorbs nutrients from the seed package until the embryo germinates and develops into a seedling that can produce true leaves and generate food through photosynthesis. All seeds encase plant embryos, which remain dormant until activated by water and climate conditions that entice germination.

Megalops of Crab

Megalops of Crab

Upon reaching the second larval stage — known as the megalops stage — the young crab has developed a body more closely resembling that of an adult, having evolved little claws and other legs similar to its progenitors. Even so, the immature crab has not yet curled and tucked under its large abdomen and thus appears to exhibit a tail, looking very much like a miniature lobster or crayfish. During this time of its life, the young crustacean continues to grow and is able to swim and crawl along the water's bottom. Eventually, after further molting, the megalops emerges into the first crab stage, looking like a small version of its adult parent.

Moss Head

Moss Antheridial Head

From zygotes, elongated structures begin to grow out of the clumps of moss. Upon reaching maximum length, the tips of these long stalks, called seta, begin to enlarge to form capsules, or sporangia. The sporangium, a spore-bearing region, contains minute, developing spores and is attached to the seta by a structure called a foot. Inside the capsule, spores develop to maturity by meiosis and are shed by wind currents and breezes.

Moss Capsule

Moss Capsule

From zygotes, elongated structures begin to grow out of the clumps of moss. Upon reaching maximum length, the tips of these long stalks, called seta, begin to enlarge to form capsules, or sporangia. The sporangium, a spore-bearing region, contains minute, developing spores and is attached to the seta by a structure called a foot. Inside the capsule, spores develop to maturity by meiosis and are shed by wind currents and breezes.

Oak Older Stem

Oak Older Stem

Like other hardwood trees, there are two kinds of wood cells: wood fibers and vessel elements. The wood fiber cells continue to grow a secondary cell wall of cellulose, hemicelluloses, and lignin, squeezing the living protoplasm and nucleus to the center of the cell until the wall is very thick and strong, and then the cells die. The vessel elements provide the transportation network for the oak tree's sap. Only in the outer layers of the vascular cambium do the phloem cells function in fluid transport. With growth, the older phloem cells are squeezed and lose function. As the tree ages, the oldest xylem cells become dead parts of a living system (like human fingernails and hair), and become the heartwood, the darker wood at the tree's center. Heartwood cells add strength and structure with their tough, fibrous mass and allow the oak to reach its tall and massive stature. The sapwood, the lighter wood, accounts for the annual rings that foresters use to estimate the age of an oak tree. The summerwood (higher density cells) form the growth rings while the springwood (the low density cells) form earlier in the year.

Oak Stem

Oak One-Year-Old Stem

Like other hardwood trees, there are two kinds of wood cells: wood fibers and vessel elements. The wood fiber cells continue to grow a secondary cell wall of cellulose, hemicelluloses, and lignin, squeezing the living protoplasm and nucleus to the center of the cell until the wall is very thick and strong, and then the cells die. The vessel elements provide the transportation network for the oak tree's sap. Only in the outer layers of the vascular cambium do the phloem cells function in fluid transport. With growth, the older phloem cells are squeezed and lose function. As the tree ages, the oldest xylem cells become dead parts of a living system (like human fingernails and hair), and become the heartwood, the darker wood at the tree's center. Heartwood cells add strength and structure with their tough, fibrous mass and allow the oak to reach its tall and massive stature. The sapwood, the lighter wood, accounts for the annual rings that foresters use to estimate the age of an oak tree. The summerwood (higher density cells) form the growth rings while the springwood (the low density cells) form earlier in the year.

Orchid Root

Orchid Aerial Root

This complex botanical ranges in size from tiny to gigantic, with species growing as tall as 25 feet (viz. Grammatophyllum speciosum). Even with such diversity, the flower on every orchid expresses bilateral symmetry, containing three petals and three petal-like, outlying sepals. Generally, there is a distinct, bottommost petal called the labellum that is larger and manifests a novel shape and color. This 'lip' contains specialized cells that secrete nectar to attract insects during reproductive pollination. Botanists theorize that many of the physical characteristics peculiar to specific orchid species have selectively evolved to attract specific pollinating insects or animals, and even include structures that so resemble female insects that the male insects try to mate with them. At the center of the flower is a structure formed by the fusion of stamens and pistil called the column.

Pine Blister Rust

Pine Blister Rust

This fungus has a rather complex life cycle: it takes up to four years to complete, requires two hosts, and involves five different types of spores. Both pine trees and the Ribes berry bushes have to be present in the environment for the fungus species to survive — pine trees can only be infected by spores that develop on the berry bushes, and the berry bushes can only be infected by spores that develop on the pine trees. Pycniospores and aeciospores are produced on the branches and stems of pines; urediniospores, teliospores, and basidiospores on currant and gooseberry foliage.

Pine Embryo

Pine Mature Embryo

Pine trees are cone-bearing evergreens found worldwide, primarily in northern temperate regions. Typically they have woody stems covered in bark, which protects tissues that conduct nutrients and water. When harvested, they provide materials like lumber, turpentine, rosin, paper, pulp, fuel and even food (pine nuts). Pines are gymnosperms, non-flowering plants that produce naked seeds not enclosed in an ovary. In many pine species, winged seeds are distributed from cones by exposure to wind or fire.

Pine Needle

Pine Needle

Pines (genus Pinus) are commonly called evergreens because they bear leaves year round, continually producing new needles as they gradually drop older ones. Characteristically, pine needles form in bundles that are spirally arranged along supporting shoots. Each bundle contains a specific number of needles associated with a particular type of tree. Pines having two or three needles in a bundle are typically hard pines. Bundles of five needles are generally characterized as soft pines.

Sclerenchyma

Sclerenchyma Stem Cells

This supporting tissue is composed of two main types of cells. The first type is the fiber cell, which is elongated and has tapering ends that can interlock with other fiber cells. These elastic, interconnected cells have great tensile strength and provide flexibility in the stem and roots. The second type, sclereid cells, are shorter and more diverse in shape, and may be found in the cortex, pith, xylem, and phloem, providing a degree of internal support for various plant organs. Sclereids are also common components in the hard coats of many seeds and the shells of nuts.

Sheep Liver Fluke

Sheep Liver Fluke

An adult liver fluke has an oval, flat body with a cephalic cone that contains the powerful oral suckers it uses to cling to and feeding off of the lining of bile ducts. In addition to producing inflammation, these parasites may release a substance that stimulates collagen production causing fibrosis in the host's tissue; such a condition may proceed to atrophy the liver and lead eventually to cirrhosis. Symptoms of worm infestation can include anaemia, severe weight loss, and low milk yields in a host sheep or cow, possibly leading to its death.

Shepherd's Purse

Shepherd's Purse Embryo

The shepherd's purse has a slender stem, clusters of tiny white flowers, and triangular seed pods (the seed pods have been said to resemble old-world leather purses). The herb bears flat, heart-shaped fruit pods, which, upon ripening, separate into two valves containing numerous yellow, oblong seeds. Additionally, it has a long history of medicinal applications and is believed to have diuretic and haemostyptic properties. A decoction yields a tannate and alkaloid called Bursine.

Shepherd's Purse

Shepherd's Purse Mature Embryos

The shepherd's purse has a slender stem, clusters of tiny white flowers, and triangular seed pods (the seed pods have been said to resemble old-world leather purses). The herb bears flat, heart-shaped fruit pods, which, upon ripening, separate into two valves containing numerous yellow, oblong seeds. Additionally, it has a long history of medicinal applications and is believed to have diuretic and haemostyptic properties. A decoction yields a tannate and alkaloid called Bursine.

Sieve Plates

Sieve Plates in Phloem

Silkworm Spiracle

The larvae feed on leaves of white mulberry, Osage orange, or lettuce, although artificial diets have been developed for modern commercial operations. After six weeks, the silkworm stops eating and spins its cocoon. The larvae possess a pair of specially-modified salivary glands called silk glands. These glands secrete a clear, viscous fluid that is forced through openings — called spinnerets — on the mouthparts of the larva. The fluid hardens as it comes into contact with air to become the silk thread. The diameter of the spinneret determines the thickness of the silk thread produced. Each cocoon of yields a strand of silk about 1,000 yards (900 meters) long.

Spider

Spider

On the spider abdomen, several silk glands hold viscous liquids that pass through minute tubes called spinnerets; normally a spider has three pairs. Upon being drawn from a droplet, the liquid protein structurally rearranges to polymerize into solid silk threads. Interestingly, once the protein leaves the gland, its molecular mass increases from 30.000 Dalton to about 300.000 Dalton to become a silk fiber. The catalyst involved in this transformation remains a mystery. The silken threads are incredibly fine — about 1/10,000 of an inch in diameter, 30 times smaller than the diameter of human hair — yet it is strong enough to stop a bee in full flight. Although spider silk is stronger than steel, the web can absorb energy that causes it to stretch, up to 140 percent of its length, without bouncing back. Even at low temperatures, the gossamer strands maintain their amazing structural properties.

Spiderwort Leaf

Spiderwort Leaf

In addition to their transcendental beauty, these prairie plants are being studied for their environmentally sensitive responses to radiation and other pollutants like pesticides. In the presence of radiation, the stamen of certain species of spiderwort are said to turn pink. Additionally, spiderwort has large chromosomes, making them ideal for specific types of genetic research. The spiderwort's botanical name, Tradescantia, is attributed to John Tradescant, who, upon returning from battling pirates on the high seas, became gardener to King Charles I of England.

Springtail

Springtail

Approximately 6,000 species of springtails exist worldwide, about 700 of which are found in North America. Most species inhabit soil and prefer a moist environment. They feed upon organic material such as fungi, bacteria, or decaying plant matter, and, in breaking down these materials, the springtails also help to enrich the soil. As a matter of fact, the presence of springtails can be used as an indicator of high soil quality.

Squash Bug

Squash Bug

The adult measures about 0.6 inches (1.5 centimeters) in length and is dark grayish-brown. In many cases, the edge of the abdomen is marked with alternating gold and brown spots. They are relatively long-lived insects, surviving an average range of 75 to 130 days, depending on availability and quality of food.

Starfish

Starfish

There are at least 1800 known species of starfish, and they occur in all the Earth's oceans (never in freshwater). The greatest variety of species is found in the northern Pacific, from the Puget Sound to the Aleutian Islands. Most starfish have five arms, but a few species have more, as many as fifty arms. These bottom-dwellers play crucial roles in the ocean ecosystem: as prey when they are free-floating larvae, and as predator when they reach adulthood. Few animals eat adult starfish, which are apparently neither palatable nor nutritious.

Sunflower Stem

Sunflower Stem

This member of the Asteraceae, or Compositae, family of flowering plants has a composite head that is supported by a series of modified leaves called the involucre. The head on the most common species of sunflower, Helianthus annuus, generally grows up to 35 centimeters in diameter and is comprised of two types of florets. Upon close examination, the large, dark disk at the center of the sunflower head is not a single appendage, but is an area comprised of many tiny, tightly-packed tubular flowers collectively called the disk flower. This type of floret takes the form of petals set in actinomorphic arrangement, being radially symmetric and generally containing pistils and stamens. The second type of floret — surrounding the disk flower — is called a ray flower. These yellow, petal-like flowers exhibit an elongated petal shape, are characterized by bilateral symmetry, and are generally sterile. Along the sunflower's tall and hairy stem are oval, coarsely-toothed leaves that are arranged in spirals.

Trichomes

Trichomes of Mullein Leaf

These accessory structures occur most often along stems and leaves, but they can also be found on the surface of petals and comprise the fragrant and sweet nectaries that draw pollinating creatures. Many forms of trichome help adjust the microclimate on the surfaces of the leaves by reflecting solar radiation and preventing evaporation of critical water supplies. Trichomes that manifest curly shapes are developed for use as reflectors by such plants as the desert brittlebush. Each variety of plant produces trichomes that are most suited to cope with the conditions of its environment. Although various forms exist, these appendages commonly occur as glandular, nonglandular, scales, papillae, or hair-like structures.

Wheat Smut

Wheat Loose Smut

Inside a seedling, parasitic smut sends out fine, thread-like filaments called hyphae that feed upon host cells. The creeping filaments form networks that invade almost all plant tissue and form an integrated structure called mycelium. Smut reproduces by forming numerous thick-walled resting spores. Upon maturity, superficial spores erupt through the confines of thin plant membranes and appear as very fine, dust-like black powder. f The minute black spores travel to other plants upon air currents or are washed into the ground to mix with seed grain during heavy dews or rain.

Wheat Rust

Wheat Rust

This fungus produces two types of fruiting bodies during its life cycle, aecia and pycnia. These structures produce different types of spores (aeciospores and pycniospores, respectively), which are transmitted from one plant to another by the wind. The pycniospores parasitize wheat while the aeciospores can infect other plants.

White Rust

White Rust of Crucifers

A. candida belongs to the phylum Oomycetes (the phylum that also includes the downy mildews and water molds). These molds produce both fertilized and asexual spores. The asexual spores (zoospores) have two whip-like flagella that enable them to move about. Infections from these spores appear as pustules or blisters. The fertilized spores (oospores) grow inside the plant tissues and cause abnormal growths, called stagheads.